It was one the most beautiful mountains in America, Mt. St. Helens, in Washington State. But what many didn't know was that this peaceful mountain had an explosive past. For more than a century, it had been quiet. But below ground, pressure had been building, and soon, Kaboom! Mt. St. Helens would erupt with terrifying fury. Eleven-year-old Sally Tanner knew the mountain well, and like many, she never imagined that this serene wilderness could turn deadly. But on May 10th, 1980, Sally finds herself in the middle of the deadliest volcanic eruption in U.S. history. Trapped on the mountain, she must escape clouds of poisonous gas, boiling rivers, and landslides of rock, glacial ice, and white-hot debris.